Knowing that the most common bacteria in bloodstream infections are also commonly found to colonize the gut without causing disease at first, researchers set out to test whether the bloodstream infections came from the gut or from the external transmission.
“This is a vulnerable population,” said senior study author Gautam Dantas, a professor of pathology & immunology at Washington University School of Medicine in St. Louis. “This is also a time when the composition of the gut microbiome is first developing. These early exposures to bacteria shape the gut microbiome in ways that will probably stay with these babies for the rest of their lives.”
The investigators studied this in newborns admitted to the neonatal intensive care units (NICU) at St. Louis Children’s Hospital, Children’s Hospital at Oklahoma University Medical Center, and Norton Children’s Hospital in Louisville, Ky.
The researchers used computational profiling to precisely track the identical strain within feces so that they could also identify the strains of bacteria that had colonized the infants’ guts prior to their bloodstream infections.
The researchers found this theory that the bloodstream infections started in the gut to be true in 58% of cases, seeing a nearly identical disease-causing bacterial strain in the gut right before a bloodstream infection was diagnosed.
Some of the strains of bacteria that caused bloodstream infections were shared among the NICU infants, the study found.
Even in controlled environments there still could be an exchange of microbes, shared by hospital staff or transferred from NICU surfaces, the study authors explained.
Yet those who had bloodstream infections had dramatically more of the species causing it in their guts in the two weeks before the infection than did NICU infants who did not have infections, the study findings showed.
The findings were published May 3 in the journal Science Translational Medicine.
Babies born prematurely are at a high risk of infections because of underdeveloped organs, according to the researchers.
Nearly all preterm babies were treated with preventive antibiotics until recently. Yet, antibiotics can lead to disruption of the gut microbiome in a way that could allow virulent strains of antibiotic-resistant bacteria to increase in numbers.
Once born, a baby’s microbiome develops as it acquires microbes from the environment and caregivers.
“From this study, as well as in our lab’s past studies, it’s clear that we need to be better stewards of how antimicrobials are given,” Dantas said. “Antimicrobials are critical; we are going to need them to treat infections, but we need to carefully weigh whether and when to use antimicrobials in specific situations. We need to make sure that when those antimicrobials are given, we have a very good reason.”
The U.S. National Institutes of Health has more on the microbiome.